COREBOXX was made to fix the filament management issue. However, storing your filaments in an enclosed chamber also enables you to control the filament's environment. I wanted to add this to COREBOXX in a Smart way. Therefore, with the help of 2 good friends, I taught myself how to design electronics. In the end, the project ended up bigger than Coreboxx itself, but I came up with what I call the Semi-Smart: a set of PCBs that combine a programmable Arduino Nano with the Prusa GPIO hackerboard neatly into 1 board. This combination enables you to achieve smart, flexible, and programmable control through the Arduino, while also allowing communication with and from the printer via the hackerboard.
This all sounds fun, but let's start with how you actually can keep filaments dry. To understand this, I first want to discuss something called Relative Humidity. A term that is often misunderstood, but crucial when it comes to keeping your spools in top shape.
To explain this term, think of air as a cup. If you have 50 ml of water in a 100 ml cup, it’s 50% full. This “fullness” is what we call Relative Humidity. It simply tells us how close the material or air is to being fully saturated with moisture.
If we then zoom in to materials like PETG or nylon, we can see they have microscopic structures that naturally wick moisture from their surroundings. This process is called hygroscopic behaviour, and it’s driven by the tendency of nature to balance things out. If you want to go deeper into this process, I recommend taking a look at LostInTech’s recent video, where he explains it very well.
But, how do we keep this from happening?? The answer is simple: we need to make sure the surrounding air has a lower relative humidity than the filament. There are two main ways we can do this: We can increase the moisture capacity of the air by heating it. Because the actual amount of present moisture stays the same, the relative humidity will drop. By keeping the temperature elevated, we can keep that relative humidity down, which ensures our filaments won't absorb moisture as quickly.
Secondly, we can remove water from the air by adding an even more hygroscopic material, like silica gel. This material has a massive tendency to hold water. When placed in the same enclosed area, it will absorb moisture from the air quicker than the filament can, which therefore keeps the Relative humidity down, and the moisture out of the filament.. With Semi-smart, we do both. We heat the air to make it less saturated, and we add silica to aggressively absorb any moisture that’s released, so it does not wick into the filament.. This means your filament stays dry, consistent, and ready for high-quality printing.
The heating itself works similarly to Bram Elema’s heated drybox. A 200W heater module kicks in when heating is needed. Then, two high-quality SUNON fans pull air through and push it out at an angle, creating steady circulation inside. To regulate the heating, there are two thermistors and one humidity sensor. On the HMI, which sits in the front, there's a sensor measuring the general temperature and humidity of the chamber. A second sensor sits right after the heater fans, measuring the output temperature of the hot air. By comparing the two, the system can smartly control both the heater and fans to reach and stabilise at the targeted temperature.
Controlling the system goes through the HMI, which stands for Human-Machine-Interface. As the name implies, this is your main point of interaction. You control everything with just three buttons: Plus, Minus, and Select. There is a small OLED screen that always displays the current temperature and humidity, as well as the state of the system. When you push a button to adjust the target temperatures, it will change the interface to show your new target, in either Celsius or Fahrenheit. Later on, this OLED can also be used to show data from your printer, like the layer number, printer chamber temperature, active spool, etc.
I also wanted to briefly talk about the importance of the word “community”, and how it helped me make the semi-smart. The whole project is only possible because of the open-source licensing and community-driven innovation philosophy that Prusa encourages. The fact that the schematics and firmware for the hackerboard are made publicly available shows that they hold great value to others, being able to build upon their work, to bring the industry forward together. This is such a huge contrast to some other brands, which sometimes don't even allow you to tinker with your own machine.
Now, don't get me wrong, competition is great and very helpful to drive innovation. However, I personally think it's better to innovate from the standpoint of wanting to bring 3D printing forward together, rather than wanting to make a quick buck or earn as much money with little effort.
Give that a thought.
Moving on, let's Talk Safety, because heating is quite a serious thing, especially with a 200W heater pulling up to 8 amps. Therefore, I want to tell you how I’ve added four layers of protection:
Firstly, there is the targeted temperature cap at 45°C. This protects the MMU, PLA spools, and COREBOXX frame from softening. You can raise it to 60°C in software if you have printed your frame, rewinders, and MMU out of a higher-temp material, but this will be at your own risk. The second stage is the Heater temperature output cap, which ensures the heater will never exceed a few degrees above the targeted temperature, with a hard limit at 50°C. This can be increased as well, at your own risk. Third in line is a mechanical Thermal fuse next to the heater, which physically cuts off the power when it exceeds 60°C. This one’s non-negotiable. And protects the heater, fans, electronics, and MMU-electronics from overheating or melting. If all of the above fail, there is a backup fuse on the PCB. It trips if the chamber temperature hits 70°C or the current exceeds 10A in case of a short or similar. This is the last line of defence and meant as a last resort when all other things go south..
Halfway through the project, I discovered I liked the electronic side of things. I just could not stop working on it, and wanted to push the Arduino and GPIO as far as I could. Now, the PCB includes many other features as well, like a RGB LED header, 2 communication lines between the GPIO and Arduino for various functions, a spare header with 2 GPIO ports, Ground and 5V connection, a quick-disconnect port for the MMU, and a servo port, although I’m not telling you what that one is for yet.
Currently, the electronics are designed specifically for the COREBOXX. However, the system is open and can be used for any enclosure you can think of, like the original enclosure for the MK3 and MK4, community versions, or in any other enclosed printer!
Then a little something about the build. I can’t expect everyone to crimp their own cables or order €200 worth of PCBs. So, just like COREBOXX itself, I worked with Blurolls to create a full electronics kit that ended up costing just €85.
The kit includes both Pre-soldered PCBs for the main unit and the HMI, all electronic components like the OLED, power supply, fans, heater, and Arduino, and all cables, pre-crimped and cut to the exact length you need.
You’ll just need to 3D print a few parts that are available for free on Printables, together with the same detailed instructions you know from Coreboxx itself. The Arduino code is published as well, together with the schematics of the PCB. If you have any programming knowledge, I encourage you to exploit those resources and add any features you now find missing! I'm so looking forward to seeing all your remixes and add-ons!
YouTube video of Semi-Smart;
COREBOXX premium on Printables: https://tinyurl.com/p5dzuphj
COREBOXX standard on Printables: https://tinyurl.com/mr57pvt5
COREBOXX Semi-Smart on Printables: https://tinyurl.com/bdhtjv9p
Semi-Smart build manual (PDF): https://tinyurl.com/ycyuv56n
BluRolls Semi-Smart Kit: https://tinyurl.com/4ycr9jub
Join the Discord community: https://tinyurl.com/mv4epj3r
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